Fluctuations in FX rates: the tax implications
You recently sold a property located overseas. You are aware that the fluctuations in currency exchange rates need to be accounted for, but are unsure about how to treat costs relating to the overseas mortgage settlement. What do you need to do?

Foreign exchange
The capital gains tax (CGT) rules require all gains or losses to be worked out in sterling. That’s to say that the purchase price of an asset must be converted to sterling at the time it was made and the sale price converted at the date it occurred. The effect is that fluctuations in exchange rates between the purchase and sale will increase or decrease the taxable amount of gain or loss. Clients are often surprised to find that taxable gains are bigger than they appear - in some circumstances, a loss may arise in the foreign currency, but this turns into a gain when the costs and proceeds are worked out in sterling. There are further complications where a mortgage is involved. This was the subject of a Tribunal case, which provides useful reference points.
The case
In Rawlings v HMRC [2022], Mr and Mrs Rawlings (R) purchased an apartment in Zermatt partly funded by a mortgage. They sold the property in 2016 and repaid the mortgage. R made a gain from the sale which they reported on their 2016/17 self-assessment returns. Their calculation reflected the change of exchange rates on purchase and sale values and also the mortgage amount. HMRC disagreed with the calculation, started an enquiry and issued an assessment to demand the additional tax it thought was due. HMRC had no issue with the foreign exchange rate changes used by R except where they related to the mortgage repayment.
Mortgages and capital gains
HMRC argued that how R financed the purchase of their property had no bearing on the calculation of the gain, which is simply the difference between the purchase price plus expenses, e.g. legal and agents’ fees, and the sales price less expenses. However, R countered that the position was different for foreign assets because the exchange rate changes resulted in an extra cost and this should be deductible from the gain. This view doesn’t seem unreasonable. In their arguments R referred to HMRC’s advice on how to calculate capital gains and losses, which says T is “a tax on the profit when you sell (or dispose of) something (an asset) at an increased value”. They stated that their “profit” was reduced because they had to pay more in sterling to clear the mortgage compared to the value of the mortgage in sterling when they took it out. This was an expense linked to the sale.
Decision
In their ruling the First-tier Tribunal judges went to some length to set out and explain the problems with the tricky calculations submitted by R. This makes the transcript relatively complicated, but this was probably to help R understand the logic of their decision, which was in favour of HMRC. While accepting that R had incurred an extra cost relating to the mortgage, the Capital Gains Tax legislation precisely sets out what expenses are allowed to be deducted when working out the amount of a gain or loss. Mortgage costs are not an allowable expense and therefore any additional cost, e.g. exchange rate losses, linked to a mortgage are also not deductible.
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